Building the Aquaponics Grow-Beds

  In the aquaponics system plants are grown typically without soil. By providing them access to nutrient and oxygen rich water the plants are able to thrive without having to waste their own resources to obtain the nutrients. So by creating an auto-siphon made from PVC pipe in a plastic bin I made my first grow bed for the plants. 

    I got a female and male adapter fittings for PVC and attached an o-ring to the end to help create a nice seal. I cut a hole out of the plastic just slightly smaller than the fitting so that I could thread into the plastic to also help provide a good seal.  

    After I tightened down the adapters together through the plastic I added silicon glue around the seams just for some extra redundancy.

    I tried very hard to ensure that it dried with the fittings positioned as vertical as possible. I just set it up real early one morning before work and so it would have all day to set, but it would have been better if I did it indoors where the humidity was lower. The silicon doesn't take to long to cure enough to be fairly rigid, but it would have done better without the humidity. 

    And here is the PVC that I used for the auto siphon and the largest piece was used for a "media-guard" which is just something to put in place to allow for easy access to the auto-siphon. It is not fun digging out all the media rocks just to clear out some roots, as I found out later when I made a grow bed without a media-guard. 

    The auto-siphon is a really nice solution for flooding and draining the grow bed. In order to provide the nutrient rich water that is highly oxygenated one much provide a fresh flow of water from the fish tank. Once the water rises to a certain point the auto-siphon drains the water out and is redirected back into the fish tank (at least in my setup).

    The auto-siphon consists of really two main parts, a stand pipe and a "bell" shroud. The standpipe is a long tube that is surrounded by a shroud. The shroud has holes cut into it low (about 2'' from the bottom) and it is large enough to provide some room for water flow in between itself and the standpipe. Once the water fills high enough it creates a siphon and do to the pressure differences forces the water out of the grow bed. The water is pushed out until the water level reaches the holes at the bottom of the shroud which allows for air to refill in the auto-siphon and breaks the siphon effect.

    It's a pretty simple idea, but it is satisfying to see in person. There is lots of troubleshooting with this system, especially if your pump does not always have the same rate of flow. You need to have enough flow to create the siphon, but if you have too much you the siphon will never break. There is lots of information available online of various methods of auto-siphoning water and plenty of guides if you're interested in building one of these systems.

    Here is a diagram from http://affnan-aquaponics.blogspot.com to help visualize the auto-siphon. 

  Here is the completed setup with the grow bed on top and plastic bin on the bottom for the temporary fish tank. I filled a majority of the grow bed up with river rocks and the rest with lava rocks. 

    I then let the system run for a week or so before I added the fish and some plants. The plastic bin I used for the grow bed had been in an outdoor garage for 5-6 years and it developed a slow leak on a corner from the expanding and contracting of the water. I then decided that a circular bin would be better for the stresses. The $6 Walmart rope bin hasn't had a problem in the seven or so months that it has been used and I expect that it will last several years since I haven't seen any wear.